The background of the enclosed invention is the same as that which is described in U.S. Pat. No. 4,488,008 in column 1, lines 1 through 63 and in U.S. patent application Ser. No. 06/710,451 entitled "Indoor Type Telephone Network Interface Device", the aforementioned patent and patent application being assigned to a common assignee, and having a common co-inventor.
Briefly stated, the invention is a telephone network interface device designed and adapted to be connected to the non-Telephone Company owned premises wiring and the Telephone Company owned portion of the subscriber loop at the juncture where the two connect one to another and may be mounted inside or outside of the owner's premises. The device provides a quick disconnect means therebetween, namely a plug and jack. The plug is mechanically and electrically engaged in the jack, thus forming an electrical circuit between the subscriber owned premises wiring and the Telephone Company owned portion of the subscriber loop. Removal of the plug from the jack disconnects the two and provides a jack into which a plug, connected to an operating telephone, may be inserted. If there is no fault in the Telephone Company owned subscriber loop portion, dial tone will be heard and the call may be made, thus indicating that any fault must be in the subscriber owned premise wiring and/or equipment. Absence of dial tone and the completed call, indicates the reverse, i.e., there is a fault in the Telephone Company owned portion of the subscriber loop.
In U.S. Pat. No. 4,488,008 entitled "Telephone Network Interface Device", there is taught a telephone network interface device, somewhat similar to and faces a problem common to that which is disclosed herein: namely, a shield member is used to cover and thus secure a portion of the cavity delimited by a backwall and a sidewall. Affixed to the backwall is a door that in its superimposed position covers the shield member and the balance of the cavity not covered by the shield. The primary purpose of the shield is to keep unauthorized personnel (non-Telephone Company employees) from entering that portion of the cavity covered by the shield (secured cavity) because in that part of the cavity are not only electronic components (half ringers and the like), but also the terminals that connect directly to the Telephone Company owned portion of the subscriber loop. Thus, the so-called secured cavity of the telephone network interface device gives rise to two problems, one of these problems having been faced by the known prior art and only partially solved and the other not faced by the known prior art.
The first problem is the one of access to the secured cavity by Telephone Company employees and prohibited access to such cavity by the premise owner. A special screw used with the shield is usually used by Telephone Companies to secure the shield to the backwall thereby making it difficult, but not impossible, for premises owners to remove the shield and thus delight themselves with the contents of the secured portion of the cavity. This secured portion not only contains the terminals that connect directly to the Telephone Company subscriber loop, but also other electronic components such as half ringers and the like; thus, intended or unintended mischief and damage can be caused to rather expensive components by untrained lay personnel giving rise to the problem to identify irrefutable evidence that an unauthorized person has made entry into the secured cavity. This problem has remained unsolved and unrecognized by the prior art. Another problem that has remained unsolved is a mechanism or device within the secured cavity that would permit the accommodation of a plurality of printed circuit boards containing electronic circuits (half-ringers and the like) of different and varying sizes.
With respect to the first-mentioned problem such is solved by a unique double door combination. Some of the prior art teaches a double door combination, but does not solve the problem of creating irrefutable evidence that there has been an unauthorized entry into a secured cavity. It is towards solution to this problem, as well as the problem of accommodating printed circuit boards of various sizes in the secured cavity, that the instant invention is directed.